Preparation of thionamides

ABSTRACT

Thionamides are formed in high yield by reacting alkyl, aryl, heterocyclic nitriles, or phenylacetonitriles and hydrogen sulfide under pressure in the presence of a minimal amount of basic catalyst. The use of a minimal amount of catalyst prevents the reverse decomposition of the thionamide to nitrile and hydrogen sulfide.

United States Patent Girgis 1 *Dec. 3, 1974 PREPARATION OF THIONAMIDES [75] Inventor: Mikhail M. Girgis, Guelph, Ontario, [56] References Cited Canada UNITED STATES PATENTS 73 Assignee; UnimyaL Ltd" Montreal Canada 3,274,243 9/1966 Gilbert ct a1 260/465.1 3,700,664 12/1972 Girgis 260/247.l Notice: The portion of the term of this patent SHbSjequEm to 1989 Primary ExaminerRichard J. Gallagher has been dlsclalmed' Assistant Examiner-Jose Tovar [22] Filed: Sept. 7, 1972 Attorney, Agent, or Firm-Willard R. Sprowls, Esq.

21 A l. N 287 173 1 PP 0 i b 57 ABSTRACT g Application Data Thionamides are formed in high yield by reacting al- [63] commumlomn'part of 23,063- March kyl, aryl, heterocyclic nitriles, or phenylacetonitriles 1970' and hydrogen sulfide under pressure in the presence of a minimal amount of basic catalyst. The use of a [52] Cl 260/2471 260/2948 minimal amount of catalyst prevents the reverse de- [511 1.... C. ..TflYi9f.'*.33????56711 39312 55,1353? hydmgc" [58] Field of Search 260/247.1, 294.8 E, 306.8,

PREPARATION OF TI-IIONAMIDES This application is a continuation-in-part of application Ser. No. 23,063. filed Mar. 26, 1970, now US. Pat. No. 3,700,664 issued Oct. 24, 1972.

. FIELD OF THE INVENTION tion of agricultural chemicals, e.g., herbicides, fungicides and insecticides.

PRIOR ART The most recent and authoritative discussion of the preparation of thionamides is Walter and Bode, Syntheses of Thiocarboxamides, Angew. Chem. lnternat. Edit. 5, 447-461 (1966) as well as the references contained therein, especially I-lurd and De La Mater, Chemical Reviews 61, 45 (1961). In the patent literature, Gilbert et al. U.S. Pat. No. 3,274,243 is pertinent. These patentees employed an amine catalyst in at least 1:10 and preferably 1:2 molecular proportions of amine: aliphatic nitrile employed in the reaction mixture, and terminated the reaction in about eight hours. The presence of the amine catalyst in the range of 10 to 50 percent with more than 100 percent excess nitrile in the reaction mixture requires that the recovery of the thionamide produced should be accomplished within 24 hours. If this is not done, the reaction product will revert to the nitrile and hydrogen sulfide gas and the 1 maximum 55 percent yield (based on the nitrile) decreases drastically.

THE INVENTION 5 l RON ms R--d NH2 In this reaction, essentially equal molar amounts of the nitrile and hydrogen sulfide are heated at 80-125 C. in the presence of a basic catalyst, the molar ratio of catalyst to nitrile being in the range from about 1:20 to 1:100. and preferably 1:80, where the nitrile is an alkyl or a carbalkoxyalkyl nitrile. Where the nitrile is an aryl-, heterocyclicor phenylacetonitrile. the molar ratio of catalyst to nitrile can be from 156.5 to 1:100, but preferably not greater than 1:30. The use of such a minimal amount of catalyst prevents the reverse decomposition warned against by Gilbert et. al. And, though Gilbert et. a1. do mention a catalyst/nitrile ratio of up to 1:10, they prefer a ratio of 1:2, and they expressly disclaim any application to aromatic and heter ocyclic nitriles.

The advantages of the present process over those of the prior art are: (1) The present process, using aliphatic nitriles, takes place without any internal (excess nitrile) or external (e.g., alcohol or xylene) solvent being required, thereby eliminating needless cost for excess material or suitable solvents and the necessity for extra procedures for their recovery. However, when aryl or heterocyclic nitriles are reacted the use of an appropriate solvent is recommended. (2) Since the level of amine catalyst in the present process is less than 1 molar percent in the reaction mixture and more than 90 percent of the nitrile has been converted to the corresponding thionamide when the starting nitrile is acetonitrile, the reaction product has been found to be stable. This eliminates the prior complex procedures for the recovery of the reaction product. (3) The reaction of the present process is completely carried out in a closed system thereby eliminating loss of materials.

The preparation of the thionamides is conveniently carried out by loading an autoclave with the required amount of catalyst and nitrile and introducing the necessary amount of hydrogen sulfide under pressure. The autoclave is heated to a temperature of 80125 C. at which temperature a pressure of 100-200 lbs. per square inch will develop. The duration of heating will vary with the nitrile but is generally 2 to 4 hours. At the end of the reaction, the autoclave is cooled, depressurized, the contents removed via a solvent and filtered. The catalyst may be removed by washing with a solvent (e.g., methylene chloride, a low boiling hydrocarbon such as benzene or xylene, or an alcohol such as isopropyl alcohol), although, when the thionamide isused as an intermediate for the synthesis of other compounds, the catalyst is present in such small amounts that it may be left in.

Suitable catalysts include ammonia, the lower alkyl primary, secondary and tertiary aliphatic amines: such as methylamine, ethylamine, isopropylamine, nbutylamine, sec.-butylamine, cyclohexylamine, benzylamine, ethanolamine. Other catalysts include sodium sulfide, potassium sulfide, tetramethylguanidine, phenylguanidine, piperidine and the secondary amines of Neiderhauser US. Pat. No. 2,870,207.

While the invention is particularly directed to the preparation of thionacetamide, it is generally applicable to the preparation of higher thionamides such as are derived from the reaction of hydrogen sulfide with: 1 Aliphatic nitriles such as propionitrile, butyronitrile, valeronitrile, or caprylonitrile, (2) Aromatic nitriles Heterocyclic nitriles such as nicotinonitrile, picolinonitrile, or N-rnorpholinonitriles, (4) Phenylacetonitriles.

EXPERIMENTAL 0 EXAMPLE 1 Acetonitrile, 164.2 g. (4.0 moles), and 3.7 g. (0.05 mole) of diethylamine were placed in a one liter stainless steel autoclave equipped with inlets for hydrogen sulfide and nitrogen, a stirrer, pressure gauge, thermocouple and recorder to record and control the temperature of the reaction. The autoclave was sealed, purged first with nitrogen (although such elimination of air fromthe reactor is not essential) and then with hydrogen sulfide. Hydrogen sulfide gas was then added until the pressure was lbs. per square inch, and this pres sure was maintained by continuous addition of hydrogen sulfide gas for 2 hours while the autoclave was heated at l00105 C. Then the autoclave was cooled to about 10 C. and depressurized. The reaction product was removed as a thick slurry in toluene, filtered, washed with chloroform and dried under vacuum at room temperature. The product thus obtained was somewhat impure, melting at 100-115 C. On recrystallization from xylene, it was obtained as white crystals melting at 112-l 16 C. The yield was 270 g. of thionacetamide (90 percent based on acetonitrile).

EXAMPLE 2 EXAMPLE 3 The procedure of Example 1 was repeated, except that 7.2 g. diisopropylamine were used and the autoclave was heated at 100-405 C. and maintained at 100 lbs. per square inch pressure for four hours. A quantitative yield of crude thionacetamide, having a melting point of 100-105 C., was obtained.

EXAMPLE 4 The procedure of Example 1 was repeated except that 14.6 g. (0.2 mole) of diethylamine were used, and the pressure of hydrogen sulfide gas was 90 lbs. per squarev inch. The temperature of the system was maintained between 85-90C. for 3 hours. The yield of product of melting point 105108 C. was 73 percent based on acetonitrile used.

EXAMPLE 5 The procedure of Example 4 was repeated. 82 g. (2 moles) of acetonitrile were reacted with hydrogen sulfide gas under 90 lbs. per square inch pressure in the presence of 14.6 g. (0.2 mole) of diethylamine. The reaction mixture was maintained at 80-90 C. for 3 hours. The yield was 82 g. representing 55 percent based on the amount of acetonitrile used.

Examples 4 and 5 demonstrate that, when the molar ratio of amine to aliphatic nitrile is increased above 1:80, the yield of the desired product falls off drastically. 1n Example 4, the molar ratio is 1:20, and in Example 5, 1:10.

EXAMPLE 6 Into a one liter stainless steel autoclave (equipped as specified in Example 1 390 g. acetonitrile (9.5 moles) were charged together with 7.1 g. (0.12 mole) of ethanolamine. The autoclave was sealed, purged with nitrogen and then with hydrogen sulfide and then 198 g. (5.8 moles) hydrogen sulfide were added to the reactor at about 5l00 C. The reaction mixture was heated gradually to 125 C. for 15 minutes, cooled to 80 C. and maintained at this temperature for 2 hours. The autoclave was cooled to 10 C., opened and the reaction product removed as a thick slurry in acetonitrile. It was filtered, washed with acetonitrile and vacuum dried at room temperature. This gave 398 g. of white crystalline thionacetamide as a residue. An additional 24 g. were recovered by distilling the unreacted nitrile. The overall yield was 93 percent based on the amount of hydrogen sulfide used. The melting point of the product was 108-1 1 1 C.

EXAMPLE 7 Using the procedure of Example 1, 64.8 g. (0.94

mole) of butyronitrile were reacted with hydrogen sulfide gas maintained at 250 lbs. per square inch pressure in the presence of 3.6 g. (0.035 mole) of diisopropylamine at 100-105 C. for about 3 hours. The autoclave was cooled to 10 C. and depressurized. The reaction product was recovered as a red-yellow oily liquid decomposing on distillation. The yield of butyrothionamide was g., corresponding to 72 percent of theory based on the nitrile employed.

EXAMPLE 8 103 g. (1 mole) of benzonitrile, 3.7 g. (0.05 mole) of diethylamine and 200 ml. absolute ethanol were placed in the stainless steel reactor of Example 1. Then, 34 g. (1 mole) of hydrogen sulfide gas were added to the reaction mixture at room temperature and the reactor was heated to C. for 2 hours. At the end of the reaction, the autoclave was cooled to 10 C. and the product was recovered by removing the alcohol on a steam bath under reduced pressure. The yield of benzothionamide melting at 1 13-1 15 C. was 133 g. or 98 percent of theory based on the nitrile used.

EXAMPLE 9 Using the procedure of Example 8, 87.8 g. (0.75 mole) m-tolunitrile were reacted with 25.5 g. (0.75 mole) hydrogen sulfide gas in the presence of 3.7 g. (0.05 mole) of diethylamine and 200 ml. ethanol at 100 C. for 2 hours. The yield of m-toluthionamide melting at 8284 C. was 98 g. or 86 percent of theory based on the nitrile used.

EXAMPLE 10 Applying the same procedure of Example 9, 53 g. (0.5 mole) of nicotinonitrile were reacted with 17 g. (0.5 mole) of hydrogen sulfide gas in the presence of 1.8 g. (0.02 mole) of diethylamine and 200 ml. ethanol at 100 C. for 2 hours. The yield of nicotinothionamide, melting at 190193 C., was 65g. or 93 percent of theory based on the amount of nicotinonitrile used.

EXAMPLE 1 l.

The procedure of Example 10 was repeated except that 53 g. (0.5 mole) of picolinonitrile were used instead of the nicotinonitrile. The yield of picolinothionamide melting at 139-141 C. was 61 g. or 87 percent of theory based on the nitrile employed in the reaction.

EXAMPLE 12 N-Morpholinonitrile, 50 g. (0.45 mole), and 7.2 g. (0.07 mole) of diisopropylamine were placed with 200 ml. of dimethyl formamide (DMF) into a 1 liter stainless steel autoclave (equipped as specified in Example 1). 17 g. (0.5 mole) of hydrogen sulfide gas were added to the reaction mixture at room temperature. Then, the reactor was heated to 80C. for 1 /2 hours. At the end of the reaction time, the autoclave was cooled to 10 C. and the product was recovered by removing most of the solvent (DMF) on a steam bath under reduced pressure. The yield of N-morpholinothionamide melting at 161 C. was 50 g., corresponding to 77 percent of theory based on the nitrile used. Analyses calculated for C H N OS: C, 41.1; H, 6.8; N, 19.2; Found: C, 41.3; H, 6.5; N, 19.3.

EXAMPLE 13 101 g. (0.86 mole) of phenylacetonitrile, 7.3 g. (0.1 mole) of diethylamine and 200 ml. ethanol were placed in the stainless steel reactor of Example 1. The reaction mixture was heated to 80 C. and hydrogen sulfide gas was added at this temperature to maintain a reaction pressure of 250 lbs. per square inch. Then, the temperature was adjusted and maintained at 120 C. for 2 hours. The thionamide was isolated by evaporating the reaction mixture on a steam bath under vacuum. The yield of phenylacetothionamide melting at 9598 C. was 93 g. or 72 percent of theory based on the nitrile employed.

EXAMPLE 14 This Example demonstrates the utility of thionacetamide.

A slurry of thionacetamide (18.7 g., 0.25 mole) in acetonitrile (200 ml.) was placed in a 500 ml. threenecked flask. The flask was equipped with a stirrer, thermometer, and reflux condenser. 54 g. (0.25 mole) of a-chloroacetoacetanilide were added and the temperature of the system was maintained between 65-70 C. with stirring for 20 minutes. The reaction mixture was cooled to about 5 C. in an ice-bath. The reaction product was removed as a slurry in acetonitrile, filtered, washed with cold water, and dried. The yield was 64 g. (95 percent of theory based on the thionamide used). The product, 5-carboxanilido-2,4- dimethylthiazole hydrochloride is a light pink crystalline material, m.p. 212214. This is a new product with broad microbiocidal activity of the types disclosed and claimed in Kulka et al., application Ser. No. 611,197 (filed Dec. 7, 1966, now U.S. Pat. No. 3,505,055 issued on Apr. 7, 1970). Analyses calculated for: C l-l Cl N OS: C, 53.6%; H, 4.8%; N, 10.4%; S, 11.9%; Found: C, 53.59; H, 4.77; N, 10.45; S, 11.87.

EXAMPLE 15 This example shows the pronounced biological activity possessed by N-morpholinothionamide.

Eight tomato plants infected with tomato early blight were isolated and treated in the following manner:

Two plants were sprayed to run off with a solution containing 2,000 ppm of N-morpholinothionamide, two plants were sprayed to run off with a solution containing 500 ppmof N-morpholinothionamide and four plants were held as a control. The results obtained were measured as percentage of control of the tomato early blightwhen compared with the four control plants.

PPM of N-Morpholino 1. In a method of preparing a benzo, o-tolu, m-tolu, nicotino, picolino, N-morpholino, or phenylacetoth- 5 ionamide, which comprises reacting a benzo, o-tolu,

m-tolu, nicotino, picolino, N-morpholino, or phenylacetonitrile with a substantially equimolar amount of hydrogen sulfide in a closed reactor at elevated temperature in the presence of a basic catalyst, the improvement which comprises conducting the re action in the presence of a mole ratio of catalyst to nitrile in the range of 1:6.5 to 1:15.

2. In a method as defined by claim 1 the improvement which comprises using a nitrogen-containing basic catalyst selected from the group consisting of ammonia, the lower aliphatic primary, secondary and tertiary amines, tetramethylguanidine, phenyl guanidine, piperidine and secondary aliphatic amines in which the aliphatic groups are alkyl or alkenyl groups of 12 to 24 carbon atoms, one of the aliphatic groups containing a tertiary carbon atom attached directly to the nitrogen atom and the other aliphatic group containing at least one carbinyl carbon atom which is not alpha or beta to the nitrogen atom. a

3. The process of claim 1, in which the reaction is conducted under a pressure of from to 200 lbs. per square inch.

4. The process of claim 1, in which the nitrile is an aryl nitrile selected from the group consisting of benzonitrile and tolunitriles.

5. The process of claim 1, in which the nitrile is nicotinonitrile.

6. The process of claim 1, in which the nitrile is picolinonitrile.

7. The process of claim 1, in which the nitrile is N- morpholinonitrile.

8. The process of claim 1, in which the nitrile is 

1. IN A METHOD OF PREPARING A BENZO, O-TOLU, M-TOLU, NICOTINO, PICOLINO, N-MORPHOLINO, OR PHENYLACETOTHIONAMIDE, WHICH COMPRISES REACTING A BENZOM O-TOLU, M-TOLU, NICOTINO, PICOLINO, N-MORPHOLINO, OR PHENYLACETONITRILE WITH A SUBSTANTIALLY EQUIMOLAR AMOUNT OF HYDROGEN SULFIDE IN A CLOSED REACTOR AT ELEVATED TEMPERATURE IN THE PRESENCE OF A BASIC CATALYST, THE IMPROVEMENT WHICH COMPRISES CONDUCTING THE REACTION IN THE PRESENCE OF A MOLE RATIO OF CATALYST TO NITRILE IN THE RANGE OF 1:6.5 TO 1:15.
 2. In a method as defined by claim 1 the improvement which comprises using a nitrogen-containing basic catalyst selected from the group consisting of ammonia, the lower aliphatic primary, secondary and tertiary amines, tetramethylguanidine, phenyl guanidine, piperidine and secondary aliphatic amines in which the aliphatic groups are alkyl or alkenyl groups of 12 to 24 carbon atoms, one of the aliphatic groups containing a tertiary carbon atom attached directly to the nitrogen atom and the other aliphatic group containing at least one carbinyl carbon atom which is not alpha or beta to the nitrogen atom.
 3. The process of claim 1, in which the reaction is conducted under a pressure of from 100 to 200 lbs. per square inch.
 4. The process of claim 1, in which the nitrile is an aryl nitrile selected from the group consisting of benzonitrile and tolunitriles.
 5. The process of claim 1, in which the nitrile is nicotinonitrile.
 6. The process of claim 1, in which the nitrile is picolinonitrile.
 7. The process of claim 1, in which the nitrile is N-morpholinonitrile.
 8. The process of claim 1, in which the nitrile is phenylacetonitrile. 